RFR: 8317262: LockStack::contains(oop) fails "assert(t->is_Java_thread()) failed: incorrect cast to JavaThread"

[David Holmes]

On Thu, 5 Oct 2023 08:41:44 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> Please review this simple fix to `LockStack::is_owning_thread()` that allows it to be called by a non-JavaThread. Thanks to @pchilano  for the regression test.
>> 
>> Testing:
>> - new regression test
>> - runtime/handshake/MixedHandshakeWalkStackTest.java
>> - tiers 1-3 sanity
>> 
>> Thanks
>
> FWIW, there's a similar static function in sychronizer.cpp:
> 
> // Can be called from non JavaThreads (e.g., VMThread) for FastHashCode
> // calculations as part of JVM/TI tagging.
> static bool is_lock_owned(Thread* thread, oop obj) {
>   assert(LockingMode == LM_LIGHTWEIGHT, "only call this with new lightweight locking enabled");
>   return thread->is_Java_thread() ? JavaThread::cast(thread)->lock_stack().contains(obj) : false;
> }
> 
> 
> There might be an opportunity to combine/reuse/deduplicate this implementation.

Thanks for looking at this @stefank !

> FWIW, there's a similar static function in sychronizer.cpp

They are not really that similar. Both are interested only in JavaThread's but one checks the current thread and the other checks a target thread.

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PR Comment: https://git.openjdk.org/jdk/pull/16047#issuecomment-1750009187